The present invention relates to a method of fabricating a semiconductor integrated circuit device and a method of fabricating a multichip module, more particularly, to a technique effectively applicable to a photolithography (hereinafter, referred to as lithography) technique in which a predetermined pattern is printed onto a semiconductor wafer (hereinafter, referred to as wafer) with using a photomask (hereinafter, referred to as mask) in the fabrication process of a semiconductor integrated circuit device.
In the fabrication of a semiconductor integrated circuit device (LSI: Large Scale Integrated Circuit), the lithography technique is used as a method of forming a fine pattern on a wafer. As the lithography technique, a so-called optical projection exposure method, in which a pattern formed on each mask is repeatedly printed onto a wafer through reduced projection optics, has become the mainstream. The basic constitution of the exposure tool is disclosed in Japanese Patent Laid-open No. 2000-91192.
The resolution R on the wafer in this projection exposure method is generally represented by: R=k×λ/NA, where k represents a constant depending on a resist material and a process, λ represents a wavelength of exposure light, and NA represents numerical aperture of a projection lens. As is apparent from the relational expression, as the pattern becomes finer, a projection exposure technique using the light source having shorter wavelength has become necessary. At the present, the LSI is fabricated by a projection exposure tool using an i-ray (λ=365 nm) of a mercury lamp or a KrF excimer laser (λ=248 nm) as an illumination light source. In order to make the pattern further finer, a light source having a shorter wavelength is required, and the employment of an ArF excimer laser (λ=193 nm) or an F2 laser (λ=157 nm) has been examined.
Meanwhile, the above-mentioned mask used in the projection exposure method has a structure in which an opaque pattern made of, for example, chromium or the like is formed as an opaque film on a quartz glass substrate transparent to an exposure light. The fabrication method thereof is, for example, as follows. That is, a chromium film serving as an opaque film is first formed on a quartz glass substrate, and a resist film reactive to an electron beam is coated thereon. Subsequently, an electron beam is irradiated onto the resist film according to pattern data predetermined, and then a resist pattern is formed by performing the development thereto. Subsequently, the chromium thin film is etched with using the resist pattern as an etching mask to form an opaque pattern made of chromium or the like. Lastly, the remaining resist film reactive to an electron beam is removed, and thus, the fabrication of a mask is completed.